Project: 4.2.5

Protecting threatened quolls and other biodiversity on Kimberley islands from cane toads

Cane toads (Rhinella marina) have caused extensive declines and local extinctions of many species on mainland Australia. Both aquatic and terrestrial species
that eat frogs or toads are highly at risk.

Australia’s islands are important conservation refuges which are rich in unique endemic species. Islands that are free from invasive species, particularly
feral animals, have also enabled some species to persist that have become extinct on the mainland. The value of islands as refuges from invasive species
has led conservation managers to use them as arks to host insurance populations of highly vulnerable mainland species.

Islands can also be especially sensitive to the impacts of invasive species, due to the naivety of local animals and the complex interrelationships
between species. The result is that invasive species can cause very large negative impacts when they reach islands and in relatively short time periods.
In combination, these factors mean that keeping cane toads off currently uninvaded Australian islands is a high priority for conservation managers.

Image: Northern Quoll. Photo: Lesley Gibson

The endangered Northern Quoll (Dasyurus hallucatus) was once widespread across Northern Australia but many local declines have been observed
following the invasion of cane toads. Northern Quolls occur on several islands across the northern Australian coast. Many islands in Queensland and
the Northern Territory have already been invaded by cane toads. The more than 2,500 islands off Western Australia’s Kimberley coast are thought to
be cane toad free, although cane toads are known to have colonised at least one island. Protecting existing quoll populations on islands is likely
to be important to the long term conservation of the species.

The ability of cane toads to breed prolifically means that, eradicating established cane toad populations is close to impossible. The greatest hope
lies in keeping cane toads off islands through biosecurity and using surveillance to eradicate single toads or very small populations before they are
able to establish. A difficulty lies in the large number of islands and the cost and logistics involved in surveillance.

Despite the significant consequences of cane toads invading islands, very little prior research has been undertaken on the distribution of cane toads
on Australia’s islands, mechanisms and risk factors associated with cane toad invasion of islands, which islands are most at risk, and which islands
have the most to lose. Filling these knowledge gaps is vital to underpin strategies and actions to protect biodiversity on Kimberley islands.

How will the research help?

This research will analyse the mechanisms and risk factors associated with cane toad invasion of Australian islands. The team will then develop a general
model of cane toad invasion for Australian islands to forecast cane toad invasion for Kimberley islands.

Guide thinking about conservation investments on islands that could be impacted by future cane toad invasions

Make decisions about toad- avoidance training of existing Northern Quoll populations on islands

The research will produce a map of Kimberley islands which includes a timeline of the expected year of toad invasion for every island, along with a measure
of certainty about the predicted date.

The research will be valuable to Kimberley island managers, especially the Traditional Owners (and their respective Ranger programs) and the West Australian
Department of Biodiversity, Conservation and Attractions, as well as the Northern Quoll Recovery Team.